Semiconductor device with capacitor insulating film and method for fabricating the same

A method for fabricating a semiconductor device having a lower electrode of impurity-doped polysilicon formed on an electrical insulating film on a semiconductor substrate, a capacitor insulating film covering said lower electrode, and an upper electrode covering said capacitor insulating film, comprising the steps of:

• forming a first silicon nitride film essentially only on a surface of said lower electrode by thermal nitriding of said lower electrode after forming said lower electrode at a predetermined position on a surface of said electrical insulating film, said electrical insulating film being formed on said semiconductor substrate;
• forming a second silicon nitride film by chemical vapor deposition to cover an entire resultant surface after a formation of said first silicon nitride film in the previous step;
• and
• forming said upper electrode to cover said second silicon nitride film.